Are energy guns practical?

Really what it'll come down to in terms of space warfare are a few factors.

1. How "stealthy" your ship is. In other words, can your ship's heat emissions and the like be spotted at 10 light years, or 1 light year? Unmanned vessels win right here because once up to speed they can basically shut everything down, and allow themselves to drop to a temperature that almost matches the background radiation temp.

2. How good your sensor systems are. Active sensors(aka radar) are nigh on useless in space because the distances are so vast that targeting would be almost impossible. You'd have to have really good passive systems.

3. The top speed/acceleration of your ship. The faster your ship can accelerate the better off you are, as that's critical in changing your direction and possibly evading incoming weapons. Having a high top speed is necessary if you actually want to get where you're going in a reasonable amount of time. Unmanned ships once again can withstand far higher accelerations and would be better at evading incoming attacks.

4. Planets are death traps. Any space faring civilization would probably live in mobile orbital habitats, and only use planets for resource gathering. Anything that has a predictable orbit, or is effectively immobile is dead meat to kinetic energy weaponry. Defending a planet is effectively futile unless you've got a fleet that can try to intercept the incoming hostiles at a long range. Even then you've got to beware of RKV attacks, since those could come from any direction, and could be launched at almost any distance provided that they were well aimed or have a way to actively maneuver.

5. No your protagonist will not own his/her own ship. Any interstellar vessel is potentially a weapon of mass destruction. Heck if a ship can do 50% light speed, and has a mass of a thousand tons or so, it's game over it strikes an inhabited world. The only people who will own ships will either be governments or massive corporations.

6. Fighters won't exist since unmanned disposable systems can do everything a fighter can do, but at half the weight, and 3x the range.

7. Combat will take a long time to actually happen, but when it happens it's over in seconds.

I disagree with a few parts here.

Dommo said:

1. How "stealthy" your ship is. In other words, can your ship's heat emissions and the like be spotted at 10 light years, or 1 light year? Unmanned vessels win right here because once up to speed they can basically shut everything down, and allow themselves to drop to a temperature that almost matches the background radiation temp.

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I'm not sure stealth really matters. Unless you have extreme weapons range, which would have to mean missiles with excellent drives, you still going to be seen a very long time before engagement range. If fights happen over maybe five lightminutes, it doesn't matter much if you can get undetected to a lightyear or only to five lightyears distance.

4. Planets are death traps. Any space faring civilization would probably live in mobile orbital habitats, and only use planets for resource gathering. Anything that has a predictable orbit, or is effectively immobile is dead meat to kinetic energy weaponry. Defending a planet is effectively futile unless you've got a fleet that can try to intercept the incoming hostiles at a long range. Even then you've got to beware of RKV attacks, since those could come from any direction, and could be launched at almost any distance provided that they were well aimed or have a way to actively maneuver.

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As discussed many times before, i don't think RKVs are actually the bee's knees. Too easy to intercept them. And it leaves aside the political issue. By the same reasoning, cities are death traps, and we still have them on earth, because intentional targeting of civilian targets is usually avoided in most (current) wars.

6. Fighters won't exist since unmanned disposable systems can do everything a fighter can do, but at half the weight, and 3x the range.

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Four times actually.

7. Combat will take a long time to actually happen, but when it happens it's over in seconds.

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I don't think so. There's no reason to hold fire until you're at a distance where you can guarantee a hit with a weapon that kills in one shot. You can start to fire from much further out, and use sandcasters, lasers with a wide focus and similar weapons that have a chance of hitting over much larger distances, but will only damage a target, not right-out kill it. Fighting at a distance where it might take you hours to take down a target with continuous fire of light weapons should often be the better choice over getting in close where it's a gamble of who hits first with an instant-kill weapon. Not to mention that it's possible to break off combat when you're at the edge of useful weapons range, and much harder to do so when you're deep within.

The reason stealth is important, is because it can tell a neighboring power, where to mobilize a fleet. Suppose it takes a few years to move your ships into position to intercept, it's a lot harder to rally a fleet of ships from a few systems if you don't know the enemy is there until they're only a year out(when it might take help a few years to arrive).

When planets are abundant(which they are), often times the condition of said planet might not be important. A life bearing planet like earth might be spared a ship ramming into it at .5 C(because the biosphere might be what makes the planet valuable), but a planet like mars, that might be just as useful ravaged(if you're mining it or something), why spare anyone? It's more of a question of economics than anything.

Dommo said:

The reason stealth is important, is because it can tell a neighboring power, where to mobilize a fleet. Suppose it takes a few years to move your ships into position to intercept, it's a lot harder to rally a fleet of ships from a few systems if you don't know the enemy is there until they're only a year out(when it might take help a few years to arrive).

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Yes, over those distances you're right. I wasn't really talking about being visible beyond a solar system. If you're visible no more than a few lightyears out, there's no time to get reinforcements over interstellar distances in, and the forces in the solar system you're targeting will have more than enough time to react, even if they only notice at a distance of one lightyear. Though another thing is military buildup i suppose. If you're noticeable a decade or so in advance, that leaves some time for really big preparations. Heck, with that timespan, building a minefield becomes feasible.

When planets are abundant(which they are), often times the condition of said planet might not be important. A life bearing planet like earth might be spared a ship ramming into it at .5 C(because the biosphere might be what makes the planet valuable), but a planet like mars, that might be just as useful ravaged(if you're mining it or something), why spare anyone? It's more of a question of economics than anything.

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Well economically, interstellar war is stupid. Raw resources are absolutely abundant in space. Fighting over planets might make sense when you're trapped in a single solar system, but not when you can go interstellar. And even intrasolar, taking the mining infrastructure intact would be a huge part of making conquering a planet worthwile in the first place. It is hard to imagine that there's not a single asteroid or oort cloud object left you could choose to simply build a new mine when you'd have to rebuild after conquering anyway. And in interstellar terms, it is even more unbelievable that you can't find an unoccupied solar system. The only interesting resource an occupied solar system has to offer is the existing infrastructure (population included), that's why it comes down to a political issue mostly. If you're fighting a genocidal war (because they are slimy insect scum that has to be wiped out before they wipe out humaty or simply because they believe in the wrong sky daddy), then bombardment it is, if you're an expanding empire, you'll want to invade to keep the infrastructure and your citizens-to-be.And not to forget, there's also the issue of people's opinions at home, wether they're willing to have their armed forces commit genocide, or not.
When we're talking human vs. human fights, i think some kind of space-geneva convention is very likely. Despite popular propaganda, there aren't actually many governments who'd be willing to risk being completely wiped out just to get a cheap shot in against a civilian target of the other side. The downside of getting completely wiped out in return is that the egomaniac in charge is dead too, and surviving usually features higher on the list of egomaniacs than going out in a blaze of glory. Suicide bombers tend not to get to the top of the ladder, downside of a short-live profession.

Oh definitely the defenders would know you're coming, there's likely no way around that. The thing is, if the defenders only have about 18 months to react, versus a decade or two, in which case are they more likely to be able to field a fleet that could possibly offer some serious resistance?

If they know you're coming, and you're 18 months out, well they're pretty well boned unless they've got a large existing defensive fleet. With 18 months time, it's simply impossible to produce a ton of war ships. In all likelihood the best bet you'd have as a defender in this case would be to evacuate your populations and move to a different system, and hope that the attackers don't have faster ships than yours.

In the latter case of 10-20 years notice, it might be possible for them to sound the alarm, in which case a nearby allied system could come to their aid. Also if they detect your fleet with that kind of time, as you said Lhun, they could definitely prepare defensively. Both of which complicate things considerably for the attacking force. I personally am not the type that'd want to attack a relatively strong system if they knew I was coming with that kind of preparation time.

Dommo said:

In the latter case of 10-20 years notice, it might be possible for them to sound the alarm, in which case a nearby allied system could come to their aid.

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Well, i'm always assuming a travel speed of well below c for "realistic" starships. Maybe 0,1c tops. Above that seems highly impractical without bolognium like shields, and imo when you want to write space opera just add a little more bolognium and go with FTL. Makes the stories much easier, and more action packed.
Anyway, i'd think of even a single lightyear as about ten years travelling time, maybe as low as five. Now that i think about that's actually interesting in terms of stealth too. If you're travelling faster, you need more energy to brake on arrival which means you're more easily noticeable. Going beyond a few g is about on the same level of bolognium as an FTL drive (since you'd need to change inertia somehow) so travelling at high fractions of c requires very long engine burn times to brake which obviously makes a ship more noticeable. Ideally, you'd want to drift into sensor range before starting the engines to break, to give minimum warning time. There's an interesting tradeoff between travelling time and visibility.

Lhun said:

This is correct in that visible range in space is extremely long, you will not start shooting as soon as you notice the other ship. Depending on the type of drive that might be a distane of lightyears, while effective weapons range would be a matter of lightseconds mostly. But the distances are still a bit large to be called "close".

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Taking a planet is always a very interesting scenario since it boils down mostly to ideology/politics on both sides. Basically, the side that controls the orbit can destroy the planet, and anything on it at will. While planets do make good platforms for some very powerful energy weapons (cooling is much easier on a planet) once those are gone, the side in orbit is in total control. But then the question arises if the inhabitants on the planet are willing to risk total destruction instead of surrendering. And if they don't surrender, are the ones in orbit willing to commit genocide to destroy the planet.[/QUOTE]
yes. Very much yes. Everyone in the whole story hates them, but no one has had the power to stand up to them. My story has a lot of open magic in it, but long story short, my MC is an immortal that has held a grudge against these guys for a very long time. And they thought they destroyed Earth but failed.

After they get all of this civilizations slaves, and taken their ships, they get a few asteroids and put them at the .8 c and slam them into their planet. the whole point of it is a genocide.

Lhun said:

Or at least some acts of terrorism, for example carpet bombing civilian areas like the allied forces did in WW2. If the attitudes on both sides are correct, you might just get a ground invasion.

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Yeah, its a ground invasion then. They don't want to surrender to some unknown power out of a little wing of the galaxy.

Lhun said:

Though one thing to keep in mind is that the invaders can always get fire support from orbit. They don't really need artillery for example, just a targeted drop of trashcans from a spaceship. If they have energy weapons that can penetrate the atmosphere, even worse for the defenders since any reasonably valuable target could be taken out easily. So no tank battles on open fields, more likely urban warfare where the light infantry dukes it out.

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those ramming troop transports are drop ready. Hit the valuable targets and get reinforcements with the same item.

Lhun said:

Nope, sorry. It's not so much the distances over which space combat is possible, or wether targeting is easy or not, but the lopsided balance between offense and defense. It's that way already with todays ships. Imagine a ship trying to ram a missile cruiser. They're going to get a cruise missile shot up their silly butts long before they have any chance of reaching ramming distance. If one good hit with a weapon will destroy a vehicle, there's no chance of getting close enough to ram. The only scenario where boarding is even remotely likely is when a ships offensive and defensive weapons have been disabled, but the crew still refuses to surrender. (And the other side doesn't just blow them up)

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That was the point of going into orbit, was to force them close. they aren't going to shoot blindly since the attacking ships are super maneuverable, and they risk hitting their own cities if they miss. The defenders are arrogant a-holes that think they are absolutely loved. They just don't comprehend the hate their attackers have for them. A few thousand dead to take their ships are so worth it for them.

Nivarion said:

That was the point of going into orbit, was to force them close. they aren't going to shoot blindly since the attacking ships are super maneuverable, and they risk hitting their own cities if they miss. The defenders are arrogant a-holes that think they are absolutely loved. They just don't comprehend the hate their attackers have for them. A few thousand dead to take their ships are so worth it for them.

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Orbit might be closer than a deep space battle, but it is not that close. Fights in actual orbit around a planet seem unlikely anyway, why wouldn't the defending force move out to intercept, and why wouldn't the attacking force try to stand off and take out all immovable installations with long range fire first? (which then forces the defenders to move out and etc.)
Anyway, the problem with ramming is that when you try to get close to ram, you will have to be able to survive a lot of fire from the ship you're trying to ram at a distance where they'd have a hard time not hitting you if they tried. And without energy shields or similar bolognium that's not going to happen. Sure, a nuke has nowhere near the destructive power of a relativistic missile, but getting a contact hit with a nuke will still destroy pretty much any ship. Maybe not if it hits the pusher plate of an orion, but who'd aim for that?
Try to imagine a scenario here on earth where a ship tries to ram and board a missile cruiser. How are they ever going to get across the hundreds of kilometres distance the cruiser can cover with his missiles without being sunk first? And in space, hundreds of kilometers is knife-fight distance.
I'm sorry to say, but ramming only makes sense if you either have some kind of super-durable shields that for some reason protect against weapons but not ramming, or if you have some kind of cloaking device than can keep a ramming ship invisible until contact, but doesn't work on missiles. Well, if it does work on missiles, ramming would be silly, but still possible i guess.
There's a good reason why ramming and boarding hasn't really been a part of naval warfare since the age of sail.

That's why I think my warships would always be unmanned. I'd rather have them scream into a system at like .5 C, and then do some intense 50 g accelerating to slow down.

Then maybe a year behind that fleet would be my manned force, which would mostly be on mop up duty since the robots should have exterminated nearly everyone.

Lhun, one thing that does make sense to me, is to instead, say use unmanned vehicles in the initial attack. They just haul ass in at like .5 C or something, and don't even slow down going through the system. They nuke the hell out of whatever they see(including using their own ships as RKV's to attack planets/ships/etc.).

Then about a week behind you've got another wave of unmanned ships that would do like a 50g deceleration, and then attack everything in sight. A few months behind them would be your manned vessels, that might assist in the mop up/or perform the invasion if a world is worth taking.

That way you don't have to give up the element of "surprise" in order to launch a devastating attack.

I have consulted my '40's Pulp magazines in hopes of restoring the Space armada to the genre!

"Generation ships" might be nice and slow moving, like fat and gold-laden Spanish galleons waddling on the stellar waves of vacuum seas and coming into a planetary system they've just 'discovered' ... only to be met by primitive rocket canoe defenses like ours!

Ha! Space Battle!

Astronauts swinging across on a rope to board the enemy ship like Errol Flynn swashbuckling as Captain Blood! Yes, there kud be scientifictional melee in our futures yet!

Dommo said:

Lhun, one thing that does make sense to me, is to instead, say use unmanned vehicles in the initial attack. They just haul ass in at like .5 C or something, and don't even slow down going through the system. They nuke the hell out of whatever they see(including using their own ships as RKV's to attack planets/ships/etc.).

Then about a week behind you've got another wave of unmanned ships that would do like a 50g deceleration, and then attack everything in sight. A few months behind them would be your manned vessels, that might assist in the mop up/or perform the invasion if a world is worth taking.

That way you don't have to give up the element of "surprise" in order to launch a devastating attack.

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I'm not all that fond of attacks at relativistic speeds, be they done with RKVs or spaceships. The fact that you pack enough ricks to allow the defenders to destroy you with absolutely anything they manage to dump in your patch seem too big a disadvantage to me.
Anyway, attacking with unmanned vessels that can accelerate high seems like the best choice, provided you have competent enough AI of course. In that case i'd imagine that all combat will be done by AIs, and human only arrive later to re-settle the system. Or take over governing it if there are survivors. If your AIs are good enough to fight autonomously i don't think there's a need for crewed combat ship at all.